Dimming control for emergency lighting systems

ABSTRACT

An emergency lighting module for providing emergency power to a solid state luminaire includes a microcontroller, and a detector coupled to the microcontroller and configured to detect a status signal indicative of a status of an AC line voltage, the emergency lighting module is configured to output a dimming control signal to the solid state luminaire in response to a reduction of the AC line voltage. The microcontroller is further configured to output a select signal to the solid state luminaire to cause the solid state luminaire to dim in accordance with the dimming control signal when the dimming control signal is output.

RELATED APPLICATIONS

The present application claims the benefit of and priority to U.S.Provisional Patent Application No. 61/569,588, filed Dec. 12, 2011,entitled “Emergency Lighting Systems And Methods For Solid StateLighting Apparatus,” the disclosure of which is hereby incorporatedherein by reference in its entirety.

FIELD

The present application relates to emergency lighting systems, and inparticular to emergency lighting systems for solid state apparatus andrelated methods.

BACKGROUND

Emergency lighting, sometimes referred to as egress lighting, islighting that is activated in the event of power loss. One purpose ofemergency lighting is to allow occupants of a building to safely exitthe building in the event of a power outage or other emergency.Emergency lighting is mandated for use in commercial buildings by manyelectrical codes. Such codes generally specify the amount of light thatmust be provided in the event of power loss and the duration of time forwhich such light must be provided. For example, U.S. building codesrequire emergency lighting to provide one footcandle of light for aminimum of 90 minutes along the path of egress during a power outage.

Emergency lighting fixtures typically have a test button whichtemporarily overrides the unit and causes it to switch on the lights andoperate from battery power even if the main AC line power is still on.Typically, the test button must be manually operated by a technician,and may be held down for the duration of the test.

In buildings, emergency lighting is commonly provided by battery-poweredemergency light fixtures that are installed in a building along with theluminaires that provide light in non-emergency situations. In somesystems, emergency lights are powered by a central bank of batteries.Building codes generally required the wiring from the central powersource to emergency luminaires to be isolated from other electricalwiring.

For fluorescent lighting fixtures, emergency operation may be controlledby an emergency ballast that includes a backup battery. A typicalfluorescent emergency lighting fixture is illustrated in FIG. 1. Thelighting fixture 10 includes an emergency ballast 12 that includes abackup battery 24. A two-lamp instant start ballast 14 is connected totwo fluorescent lamps 16A, 16B. A test switch 18 permits manualactivation of the emergency ballast 12.

As is known in the art, fluorescent lamp ballasts stabilize the currentthrough fluorescent lamps, which have a negative resistancecharacteristic. The ballast provides a positive resistance or reactancethat limits the current through the fluorescent lamp to an appropriatelevel. An instant start ballast, such as the ballast 14, starts thelamps 16A, 16B without heating the cathodes of the lamps by generating ahigh initial voltage (around 600 V).

A fluorescent emergency lighting system can also be configured so thatthe emergency ballast 12 serves the function of both providing regularillumination and emergency lighting without the need for a separate lampballast.

SUMMARY

An emergency lighting module for providing emergency power to a solidstate luminaire according to some embodiments includes amicrocontroller, and a detector coupled to the microcontroller andconfigured to detect a status signal indicative of a status of an ACline voltage. The emergency lighting module is configured to output adimming control signal to the solid state luminaire in response to thestatus signal.

The microcontroller may be further configured to output a select signalto the solid state luminaire to cause the solid state luminaire to dimin accordance with the dimming control signal when the dimming controlsignal is output.

The microcontroller may be configured to cause the solid state luminaireto select from among step dimming, 0-10V dimming and/or digitaladdressable lighting interface (DALI) dimming using the select signal.

The microcontroller may be configured to cause the solid state luminaireto select from among step dimming, 0-10V dimming, digital addressablelighting interface (DALI) dimming, and/or pulse width modulation (PWM)dimming using a PWM signal generated by the emergency lighting moduleusing the select signal.

The status signal may indicate a reduction or interruption of the ACline voltage.

The emergency lighting module may be further configured to output a stepdimming control signal to the solid state luminaire in response to thepresence or absence of one or more AC line input signals.

The emergency lighting module may further include an AC filter coupledto the detector and may be configured to supply a filtered AC signal tothe detector. The AC filter may be configured to output the step dimmingcontrol signal to the solid state luminaire.

The emergency lighting module may further include an input configured toreceive an external dimming signal and to generate the dimming controlsignal in response to the external dimming signal when no reduction ofthe AC line voltage is detected.

The dimming control signal may include a pulse width modulation (PWM)signal.

The emergency lighting module may further include a digital addressablelighting interface (DALI) interface configured to receive a DALI dimmingsignal, the external dimming signal includes the DALI dimming signal.

The external dimming signal may include a 0-10V signal or a step dimmingsignal.

The emergency lighting module may further include a plurality of ACdetectors configured to detect a presence or absence of a plurality ofswitched AC line voltage signals and to generate the step dimming signalin response to the presence or absence of the plurality of switched ACline voltage signals.

The emergency lighting module may further include an analog to digitalconverter configured to receive the 0-10V signal and to responsivelyoutput a digital signal indicative of the 0-10V signal to themicrocontroller.

An emergency lighting module for providing emergency power to a solidstate luminaire according to further embodiments includes amicrocontroller, and an AC detector coupled to the microcontroller andconfigured to detect a presence of an AC line voltage. The emergencylighting module is configured to output a dimming control signal to thesolid state luminaire in response to a reduction of the AC line voltage.The module further includes an input configured to receive an externaldimming signal and to generate the dimming control signal in response tothe external dimming signal when no reduction of the AC line voltage isdetected.

An emergency lighting module for providing emergency power to a solidstate luminaire according to further embodiments includes amicrocontroller, a plurality of inputs configured to receive a pluralityof external dimming signals, and a dimming control output coupled to thesolid state luminaire. The microcontroller is configured to generate adimming control signal and to output the dimming control signal to thesolid state luminaire in response to a selected one of the externaldimming signals.

Other systems, methods, and/or computer program products according toembodiments of the invention will be or become apparent to one withskill in the art upon review of the following drawings and detaileddescription. It is intended that all such additional systems, methods,and/or computer program products be included within this description, bewithin the scope of the present invention, and be protected by theaccompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate certain embodiment(s) of theinvention. In the drawings:

FIG. 1 is a schematic diagram of a conventional fluorescent lightingfixture with an emergency lighting ballast.

FIG. 2 is a schematic diagram of a solid state luminaire coupled to apower inverter.

FIG. 3 is a schematic diagram of an emergency lighting module for asolid state luminaire according to some embodiments.

FIGS. 4 and 5 are schematic diagrams of emergency lighting modules forsolid state luminaires according to further embodiments.

FIGS. 6 and 7 are detailed schematic diagrams of emergency lightingmodules according to some embodiments.

FIG. 8 is a circuit diagram of a buck converter for an emergencylighting module according to some embodiments.

FIG. 9 is a circuit diagram of a boost converter for an emergencylighting module according to some embodiments.

FIG. 10 is a detailed schematic diagram of an emergency lighting moduleaccording to further embodiments.

FIG. 11 is a circuit diagram of a bidirectional boost/charge convertercircuit for an emergency lighting module according to some embodiments.

FIGS. 12A-12C are schematic diagrams of circuits according to someembodiments for identifying a battery that is connected to an emergencylighting module.

FIG. 13 is an exploded perspective view illustrating some mechanicalaspects of a luminaire enclosure according to some embodiments.

FIG. 14A to 14C are graphs of voltage versus time for voltages generatedby an emergency lighting module and a solid state lighting moduleaccording to some embodiments.

FIGS. 15A-15C are schematic diagrams of circuits according to someembodiments for identifying a luminaire that is connected to anemergency lighting module.

FIG. 16 is a graph of duty cycle versus time for pulse width modulateddimming signal generated by an emergency lighting module according tosome embodiments.

FIG. 17 is a flowchart that illustrates systems/methods for performingemergency lighting tests by an emergency lighting module according tosome embodiments.

FIGS. 18A-18D are schematic diagrams illustrating variousapparatus/methods for wireless actuating a test switch of an emergencylighting module according to some embodiments.

FIGS. 19-21 are schematic diagrams of emergency lighting modules andsolid state luminaire power boards that are configured to implementvarious types of dimming functions in accordance with some embodiments.

FIG. 22 is a block diagram of an AC detector according to someembodiments.

FIG. 23 is a graph of charging voltage versus charging current for arechargeable backup battery for an emergency lighting module inaccordance with some embodiments.

DETAILED DESCRIPTION

Embodiments of the present invention now will be described more fullyhereinafter with reference to the accompanying drawings, in whichembodiments of the invention are shown. This invention may, however, beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein. Rather, these embodiments areprovided so that this disclosure will be thorough and complete, and willfully convey the scope of the invention to those skilled in the art.Like numbers refer to like elements throughout.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, these elements should notbe limited by these terms. These terms are only used to distinguish oneelement from another. For example, a first element could be termed asecond element, and, similarly, a second element could be termed a firstelement, without departing from the scope of the present invention. Asused herein, the term “and/or” includes any and all combinations of oneor more of the associated listed items.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises,”“comprising,” “includes” and/or “including” when used herein, specifythe presence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms used herein should be interpreted ashaving a meaning that is consistent with their meaning in the context ofthis specification and the relevant art and will not be interpreted inan idealized or overly formal sense unless expressly so defined herein.

Recently, solid state luminaires that use light emitting diodes (LEDs)as light sources instead of fluorescent bulbs have been developed forgeneral illumination. Accordingly, there is a need for emergencylighting systems that are suitable for driving an LED load.

Conventionally, emergency lighting for solid state luminaires has beenhandled through the use of a battery powered inverter connected to theluminaire. For example, as shown in FIG. 2, an inverter 28 is coupled toa solid state luminaire 26. The inverter includes a battery (not shown)that is charged by power received from an AC input (AC_IN) that alsonormally powers the luminaire 26. As is known in the art, an invertergenerates a sine wave or quasi-sine wave AC output in response to a DCpower signal, such as a DC signal generated by a battery. The inverter28 monitors the input voltage AC_IN and supplies an AC signal to theluminaire 26 in the event the AC_IN voltage is removed. One drawback ofthis type of system is that the solid state luminaire 26 is unaware ofthe power outage, and will continue to run at its full lumen level.Thus, in order to meet applicable code requirements, the inverter mustbe capable of supplying enough power to run the luminaire 26 at its fulllumen output level for the entire time period required by code. Thisundesirably increases the capacity requirements, and therefore the cost,of the battery.

Embodiments of the present invention provide an emergency lightingmodule that provides DC power to a solid state luminaire and thatcontrols operation of the luminaire in an emergency lighting mode. Someembodiments may also control dimming of the luminaire in a non-emergencymode. Referring to FIG. 3, an emergency lighting module 32 providesemergency power to a solid state luminaire 35. The emergency lightingmodule 32 connects directly to the LED array 34 of the luminaire 35 aswell to an AC LED driver 30, and provides a DC voltage signal DC_OUT tothe LED array 34. It will be appreciated that the emergency lightingmodule 32 and/or the AC LED driver 30 may be provided together with theLED array 34 as an integral part of an LED display or as separatecomponents. Moreover, the LED array 34 may have any desiredconfiguration and/or number of LEDs, including only a single LED.

In normal operation, an LED driver provides DC current to an LED array.As power is typically supplied via AC lines, it must be converted to DC.Referring to FIG. 3, AC power is supplied via the AC_IN line. The ACpower is passed to the AC LED driver 30, which generates a DC drivesignal DC_IN that is passed to the LED array 34 through the emergencyLED driver 32 over the DC_OUT line.

When the AC power supplied over the AC_IN input is interrupted, DC poweris drawn from an auxiliary source 36, which may be a rechargeablebattery pack, and passed to the LED array 34 over the DC_OUT line.

This configuration is an improvement over the configuration shown inFIG. 2 that uses an inverter to supply emergency AC power, as theemergency lighting module 32 can directly drive the LEDs with DC powerat a lower current in the event of a power outage. However, in such aconfiguration, the emergency LED driver current is set at a fixed level.Thus, the lumen output of the luminaire 35 may vary depending on theconfiguration of the particular luminaire that the emergency module 32is paired with. For example, if the luminaire 35 has 10 LEDs with adrive current of 1 amp, the lumen level output by the luminaire 35during emergency operation will be different than the lumen output of aluminaire that has 10 LEDs with a drive current of 750 milliamps,because both luminaires would be run at the same reduced load current inemergency operation.

Some embodiments of the present invention provide digitally controlledemergency lighting modules (ELMs). Digital control may be accomplishedby means of a microcontroller, a microprocessor, a field programmablegate array, or other suitable digital circuitry. The term“microcontroller” is used herein to refer to any suitably configureddigital control circuitry. Microcontrollers are commonly employed in LEDlighting systems for dimming control via remote communications. Someembodiments of the present invention provide a microcontroller basedemergency lighting module for solid state luminaires in which amicrocontroller performs emergency monitoring and control functions inaddition to dimming control.

In an emergency lighting module according to some embodiments, themicrocontroller and its firmware can provide comprehensive systemmonitoring and control functionality. Several semi-autonomous controlsystems/algorithms may be merged together to implement the systemrequirements.

Inclusion of a microcontroller in and emergency lighting module (withits accompanying input/output, peripherals, and firmware-basedalgorithms) allows for more sophisticated and integrated control thanwould otherwise be practical.

With a microcontroller and its associated input/output (I/O) capabilityand design flexibility, an emergency lighting module according to someembodiments may have the capability of handling multiple feature setsand technologies within the same product.

Emergency lighting modules according to embodiments of the invention areillustrated in FIGS. 4 and 5. Referring to FIGS. 4 and 5, an emergencylighting module 100, 100′ is connected to and provides emergency powerto a solid state luminaire 70. The solid state luminaire 70 includes anAC/DC converter 40, 40′ an LED control module 50 and an LED board 60.

The AC/DC converter 40 of FIG. 4 receives a rectified AC signal andresponsively generates a DC output signal DC_IN. The AC/DC converter 40′of FIG. 5 receives a power line AC input signal, which may, for example,be an AC signal at 120 or 220 volts, and responsively generates a DCoutput signal while passing the AC input signal on to the emergencylighting module 100. The DC output signal of the AC-DC converter 40, 40′is provided to an LED control module 50. The LED control module 50performs DC/DC conversion to generate a DC signal that is configured todrive LEDs in the LED board 60 at a desired level. The LED controlmodule 50 may control the brightness and/or hue of light emitted by theLED board 60 by controlling the voltage and/or current supplied tovarious LEDs or groups or strings of LEDs in the LED board 60 via theLED DRIVE input to the LED board 60.

The LED board 60 may include single and/or multiple strings of white,red, blue, green and/or blue-shifted yellow (BSY) LEDs as described forexample in U.S. Pat. No. 7,213,940 and U.S. Pat. No. 8,029,155 thedisclosures of which are incorporated by reference in their entirety.

Referring to FIG. 4, the emergency lighting module 100 receives an ACline voltage signal AC_IN and responsively generates a rectified ACsignal, which is provided to the AC/DC converter 40. The emergencylighting module 100 also receives the DC_IN signal from the AC/DCconverter 40, which is used to charge a backup battery 120 (FIG. 6). Theemergency lighting module 100 further generates an ON/OFF control signaland a pulse width modulation (PWM) dimming signal PWM_OUT, which areapplied to the LED control module 50 to control the operation thereof.The emergency lighting module 100 is also configured to generate aDC_OUT signal that is used to drive the LED control module 50 when theAC input signal is lost.

The DC_OUT signal generated by the emergency lighting module 100 and theDC_IN signal generated by the AC/DC converter 40, 40′ are rectified bydiodes 72, 74 before being applied to the LED control module 50.Accordingly, a higher of the voltages DC_IN, DC_OUT is applied to theLED control module 50.

The emergency lighting module 100 also receives a module type signal MTthat indicates the type and/or identity of the luminaire 70 to which theemergency lighting module 100 is attached. The emergency lighting module100 may use the module type information to determine how much theluminaire 70 should be dimmed during emergency operation to meet minimumluminescent requirements for emergency lighting, as discussed in moredetail below.

Referring to FIG. 5, the emergency lighting module 100′ receives an ACsignal from the AC/DC converter 40′ and a DC_IN signal from the AC/DCconverter 40′. The emergency lighting module 100 further generatesON/OFF control and PWM_OUT dimming signals, which are applied to the LEDcontrol module 50. The emergency lighting module 100 is also configuredto generate a DC_OUT signal that is used to drive the LED control module50 when the AC input signal is lost.

An emergency lighting module 100 according to some embodiments isillustrated in more detail in FIG. 6. As shown therein, the emergencylighting module 100 includes a microcontroller 110 that controlsoperations of the emergency lighting module 100.

The microcontroller 110 may include, but is not limited to, aprogrammable microcontroller, microprocessor, field programmable gatearray, or other suitable circuitry. In particular, the microcontroller110 may be a general purpose programmable microcontroller, such as amodel MSP430 microcontroller manufactured by Texas Instruments.

A conventional AC filter 114 filters and rectifies an AC line voltageAC_IN. The rectified AC signal is output by the AC filter 114. An ACdetector 112 is coupled to the AC filter 114 and detects the presence orabsence of an AC input signal to the AC filter 114. An output of the ACdetector 112 is provided to the microcontroller 110.

Brief reference is made to FIG. 22, which illustrates an AC detector 112according to some embodiments in more detail. As shown therein, the ACdetector may include a rectifier circuit 111 having an input coupled tothe AC filter 114 and an output coupled to a comparator 113 that drivesan opto-coupler 115 for providing a signal Si that is indicative of theAC line voltage. The opto-coupler 115 output will pulse at the linefrequency rate as long as the AC voltage magnitude is above apredetermined cutoff level Vref. When the AC voltage drops below thecutoff level, the comparator 113 output becomes static, and no furtherpulses are generated through the opto-coupler 115. The microcontroller110 monitors the opto-coupler output signal for activity. If theopto-coupler output stops producing transitions at the line frequency,the microcontroller 110 may detect this as a loss of AC signal.

Referring again to FIG. 6, the microcontroller 110 is also coupled to abattery charger 116 and a voltage booster 118, and controls operationsthereof. A DC input is provided to the battery charger 116, while a DCoutput voltage DC_OUT is provided by the voltage booster 118. Thevolatile and non-volatile memory requirements for the microcontroller110 may be fulfilled with internal and/or external circuitry. Thedigital controller may use internal and/or external devices to convertanalog and digital input/output signals.

A battery 120 is coupled to the microcontroller 110, the battery charger116 and the voltage booster 118. The battery 120 may be a rechargeablebattery, which may in some embodiments include a lithium-iron-phosphate(LiFePO₄) rechargeable battery cell. Other types of battery technologiesmay be use, including, without limitation, NiCd, NiMH, lead-acid, etc.The battery 120 may be provided externally to the emergency lightingmodule 100 as illustrated in FIG. 4, or may be integrated within theemergency lighting module 100.

The battery 120 provides a battery type signal BT that indicates thetype of battery that is connected to the emergency lighting module 100.The microcontroller 110 may use this information to determine thebattery type, voltage and/or capacity (e.g., in milliamp-hours) of thebattery 120.

The battery 120 and/or the emergency lighting module 100 may include atemperature sensor 125 that provides a temperature signal TEMP that isrepresentative of the temperature of the battery 120 to themicrocontroller 110. The temperature of the battery 120 may be used bythe microcontroller to improve the safety of the battery packs and alsoto improve charging performance. Using the temperature information itmay be possible for the microcontroller 110 to tailor charging anddischarging functions to increase efficiency for a given temperature.The microcontroller 110 may also disable the battery pack 120 inresponse to a temperature sensed by the temperature sensor 125 in theevent of a malfunction.

An exemplary charging algorithm is illustrated in FIG. 23, which is agraph of charging voltage versus charging current. Assuming a dischargedbattery has a discharged voltage level of V1, the battery is charged byapplying a constant current I2 to the battery. In response to thecharging current, the battery voltage may rise from V1 to V2 while thecharging current is held constant. Once the battery voltage reaches acharged voltage level of V2, the battery voltage is held constant, whilethe charging current is reduced from I2 to I1.

The values of I1, I2, V1 and V2 may be determined or selected inresponse to a temperature sensed by the temperature sensor 125. Thedetermination may be made, for example, using a formula, a lookup table,etc. In particular embodiments, the values of I1 and I2 may be reducedwhen a high temperature is detected and increased when a low temperatureis detected. Moreover, charging could be suspended if a temperaturehigher than a threshold temperature is detected. After a temperaturebased shutoff, charging may be retried after waiting a predefined periodof time and/or waiting until the sensed temperature falls below a secondthreshold level.

Referring again to FIG. 6, the microcontroller 110 has an input for atest switch and an output for battery status. The microcontroller 110also generates the ON/OFF control and PWM_OUT dimming signals describedabove.

The microcontroller 110 is configured to monitor the status of the ACdetector 112, and, in response to a detected loss of AC input power,cause the voltage booster 118 to generate a DC output voltage DC_OUT tobe supplied to the LED control module 50. The microcontroller 110 alsocontrols the level of light output by the solid state luminaire 70 bymeans of a PWM_OUT dimming signal.

An emergency lighting module 100′ according to some embodiments isillustrated in more detail in FIG. 7. The emergency lighting module 100′shown in FIG. 7 is similar to the emergency lighting module 100 shown inFIG. 6, except that the emergency lighting module 100′ includes an ACdetector 112′ that receives a rectified AC signal and responsivelygenerates a signal indicative of the status of the AC power supply,which is provided to the microcontroller 110.

As noted above, the AC/DC converter 40, 40′ in the luminaire 70 (FIG.4-5) converts AC voltage to a DC voltage which is delivered to the DC/DCLED control module 50. The LED control module 50 converts the DC inputvoltage to a controlled and regulated current for driving single ormultiple LED strings in the LED board 60.

In the configuration illustrated in FIG. 7, the emergency lightingmodule 100′ receives an AC signal as an input. The AC signal ismonitored for indication of loss of AC power for transition to backupoperation and for charging the battery 120. The microcontroller 110detects the absence of an AC signal and in response transitions toemergency lighting mode. When emergency lighting mode is entered, themicrocontroller 110 shuts off the AC/DC converter 40 via the ON/OFFcontrol signal and delivers a pulse width modulated signal PWM_OUT tothe LED control module 50 which determines the lumen level output by thefixture in an emergency mode. The microcontroller 110 also causes thevoltage booster 118 to deliver a DC voltage DC_OUT to the LED controlmodule 50. This level of integration allows the reuse of existingelectronics on the luminaire 70, such as the DC/DC circuitry in the LEDcontrol module 50 and the AC/DC rectifiers in the AC/DC converter 40.That is, only a single AC/DC converter and a single DC/DC LED controlcircuit may be needed between the emergency lighting controller 100 andthe luminaire 70.

Some existing fluorescent and LED emergency fixtures include a detectioncircuit that senses brown out conditions (as opposed to complete powerloss conditions) that may cause a luminaire to go out even though the ACpower has not completely gone away. It may be desirable for theemergency lighting to engage during brownout conditions to keep thelight output at minimum levels.

According to some embodiments, the microcontroller 110 can monitor thesecondary side DC voltage (DC_IN signal in FIGS. 4 and 5) that powersthe LED strings. When this voltage begins to dip (indicating a potentialbrown-out condition), the digital controller can switch to emergencymode to ensure light output during brown outs that may cause othernon-emergency LED lights to go out. Accordingly, as illustrated in FIGS.6 and 7, the DC_IN signal may be provided to an analog to digitalconverter input ADC of the microcontroller 110, which allows themicrocontroller 110 to monitor the level of the DC_IN voltage generatedby the AC/DC converter 40.

The battery charger 116 may be implemented as a buck converter asillustrated, for example, in FIG. 8. As shown therein, the batterycharger 116 may include input and output capacitors C1, C2, a transistorQ1, which may be a N-channel enhancement mode MOSFET, a diode rectifierD1 and an inductor L1. It will be appreciated that the transistor Q1could be any type of suitably configured current or voltage controlledswitch, such as p-channel MOSFETs, bipolar junction transistors, etc. Aninput voltage DC_IN is drawn from the AC/DC converter 40, 40′ of theluminaire 70, as illustrated in FIGS. 4 and 5. An output voltage VCHG isprovided to the battery 120. The voltage generated by the AC/DCconverter 40, 40′ of the luminaire 70 is typically much higher than thevoltage needed to charge the battery 120. Accordingly, the batterycharger 116 steps the voltage down to provide a desired voltage levelVCHG for charging the battery 120.

The operation of a buck converter is well known. Referring again to FIG.8, the transistor Q1 is operated as a switch under control of themicrocontroller 110, which monitors the output current and voltage ofthe battery charger 116 and responsively controls the ON/OFF state ofthe transistor Q1 through a control signal CTRL1 applied to the gate ofthe transistor Q1. By controlling the ON/OFF state of the transistor Q1,the buck charger circuit alternates between connecting the inductor L1to the source voltage DC_IN to store energy in the inductor L1 when thetransistor Q1 is in the ON (conductive) state, and discharging theinductor L1 into the output capacitor C2 (using current drawn throughthe rectifying diode D1) when the transistor Q1 is in the OFF(nonconductive) state. By measuring the output voltage VCHG, themicrocontroller 110 can control the switch Q1 to have a duty cycle thatmaintains a constant output voltage on the output capacitor C2. As iswell known in the art, “duty cycle” of a pulse train refers to the ratioof the pulse duration to the pulse period.

Conversely, during emergency operation, it is necessary to boost theoutput voltage VBATT provided by the battery 120 so that it can be usedby the luminaire to drive the LED control module 50. The voltagegenerated by the battery VBATT must therefore be boosted to the samevoltage level that would otherwise be provided by the AC/DC converter40, 40′ of the luminaire before it can be output as a DC_OUT voltagesignal.

Accordingly, the voltage booster 118 may be implemented as a boostconverter as shown in FIG. 9. A boost converter is a DC/DC converterthat boosts an input voltage to a higher voltage level. Referring toFIG. 9, the voltage booster 118 may include an input capacitor C3, anoutput capacitor C4, a transistor switch Q2, which may be an N-channelenhancement mode MOSFET, a diode D2 and an inductor L2. It will beappreciated that the transistor Q2 could be any type of suitablyconfigured current or voltage controlled switch, such as p-channelMOSFETs, bipolar junction transistors, etc.

An input voltage VBATT is provided from the battery 120, and the boostconverter generates an output voltage DC_OUT that is provided to the LEDcontrol module 50, as shown in FIGS. 4 and 5.

The state of the transistor switch Q2 is controlled by themicrocontroller 110 via a gate control signal CTRL2 applied to the gateof the transistor Q2.

By controlling the ON/OFF state of the transistor Q2, the boostconverter 118 causes the charge on the output capacitor C4 to increaseto a higher level than the input voltage VBATT due to the tendency ofthe inductor L2 to resist changes in current. When the transistor Q2 isin the ON (conductive) state, current through the inductor increasesrapidly, causing the inductor L2 to absorb energy, which is stored inthe magnetic field of the inductor. When the transistor Q2 is switchedto an OFF (nonconductive) state, the inductor L2 discharges storedenergy through the diode D2 and into the output capacitor C4. Thevoltage generated by the inductor L2 during the discharge phase isrelated to the rate of change of current, and not to the originalcharging voltage, thus allowing the output voltage DC_OUT that is storedon the output capacitor C4 to exceed the input voltage VBATT.

By monitoring the output voltage DC_OUT, the microcontroller 110 cancontrol the transistor Q2 to have a duty cycle that causes the outputvoltage DC_OUT to remain at a desired voltage level.

Referring to FIG. 10, in some embodiments, the boost and chargingcircuits can be combined into a single bidirectional booster/charger 168that acts to both charge the battery 120 under normal operatingconditions and supply a DC voltage to the LED controller 40, 40′ inemergency operation.

Operation of the bidirectional booster/charger 168 is controlled by twocontrol signals CTRL3 and CTRL4 generated by the microcontroller 110. Innormal operation, the bidirectional booster/charger 168 acts as abattery charger. In particular, in normal operation, the bidirectionalbooster/charger 168 receives a DC input voltage DC_IN at terminal T1 andprovides a charging voltage VCHG to the battery 120 at terminal T2. Inemergency mode, the bidirectional booster/charger 168 acts as a voltagebooster, in which case the bidirectional booster/charger 168 receives abattery voltage signal VBATT at terminal T2 and provides a DC outputvoltage DC_OUT to the LED control module 50 at terminal T1.

FIG. 11 is a circuit diagram of a bidirectional booster/charger 168according to some embodiments. The bidirectional booster/charger 168includes switching transistors Q3, Q4, which may be n-channelenhancement mode MOSFETs, although other types of suitably configuredtransistor switches can be used, including p-channel MOSFETs, bipolarjunction transistors, etc. The bidirectional booster/charger 168 furtherincludes capacitors C5, C6 and an inductor L3. A first input/outputterminal T1 and a second input/output terminal T2 are provided.

In the bidirectional booster/charger 168, the power moves eitherdirection based on how the switching transistors Q3, Q4 are driven.There are a number of challenges to implementing this circuiteffectively. The challenge first is being able to control the voltagesin each direction. The two circuit topologies (charger and booster) havevery different transfer characteristics requiring what amounts to twoseparate control loops. These two loops then have to work togetherseamlessly based on which direction it is desired for the power to move.

The microcontroller 110 monitors the voltage and current at each end ofthe booster/charger 168 and drives the transistor switches Q3, Q4directly in response to the measured voltages and currents. In such animplementation, control of the transistor switches can be implemented insoftware, which enables the microcontroller to customize the operationof the booster/charger 168 based on the type of luminaire and/or batteryto which the emergency lighting module 100 is connected.

The transistors Q3 and Q4 are operated as switches under control of themicrocontroller 110, which controls the ON/OFF state of the transistorsQ3 and Q4 through control signals CTRL3 and CTRL4 applied to the gatesof the transistors Q3, Q4, respectively.

In charging mode (normal operation), the circuit sees a voltage appliedat terminal T1 and a load at terminal T2. In that case, the circuitsteps the voltage level down from T1 to T2. When the transistor switchQ3 is in the ON (conductive) state and the transistor switch Q4 is inthe OFF (nonconductive) state, the inductor L1 is connected to thesource voltage DC_IN and energy is stored in the inductor L1. When thetransistor switch Q3 is switched to the OFF (nonconductive) state, thetransistor Q4 is switched to the ON (conductive) state, and energy isdischarged from the inductor L1 into the output capacitor C6 usingcurrent drawn through the conducting switch Q4. Accordingly, in chargingmode, the transistors Q3 and Q4 are driven with complementary controlsignals at a selected duty cycle Dchg.

By measuring the output voltage VCHG, the microcontroller 110 cancontrol the switches Q3, Q4 to have duty cycles that maintain a constantoutput voltage on the output capacitor C6.

In charging mode, the output voltage VCHG is related to the inputvoltage DC_IN according to the following formula:

VCHG=Dchg*DC_IN  [2]

In the boost mode (emergency operation), the circuit sees a voltageapplied at terminal T2 and a load at terminal T1. In that case, thebidirectional booster/charger 168 causes the charge on the outputcapacitor C5 at terminal T1 to increase to a higher level than the inputvoltage VBATT applied at the terminal T2. When the transistor Q4 is inthe ON (conductive) state and the transistor Q3 is in the OFF(nonconductive) state, current through the inductor L3 increasesrapidly, causing the inductor L3 to absorb energy, which is stored inthe magnetic field of the inductor. When the transistor Q4 is switchedto an OFF (nonconductive) state and the transistor Q3 is switched to theON (conductive) state, the inductor L3 discharges stored energy into thecapacitor C5, which serves as an output capacitor in the boost mode.Accordingly, in boost mode, the transistors Q3 and Q4 are driven withcomplementary control signals at a selected duty cycle Dboost.

The voltage generated by the inductor L3 during the discharge phase isrelated to the rate of change of current through the inductor, and notto the original charging voltage, thus allowing the output voltageDC_OUT that is stored on the output capacitor C5 to exceed the inputvoltage VBATT. In boost mode, the output voltage DC_OUT is related tothe input voltage VBATT according to the following formula:

DC_OUT=VBATT/Dboost.  [2]

The charging subsystem of the emergency lighting module 100 includes thecharger power supply electronics (i.e., the voltage charger 116 orbidirectional booster/charger 168), the microcontroller 110, ananalog-to-digital converter (ADC), and a Pulse Width Modulation (PWM)output generator. The ADC and the PWM generator maybe implemented withinthe microcontroller 110 and/or as peripheral elements coupled to themicrocontroller 110.

The voltage charger 116 or bidirectional booster/charger 168 providesthe voltage and current needed for the charging process. Themicrocontroller 110 monitors both the charging voltage and the chargingcurrent via the ADC. The microcontroller 110 monitors the ADC values,and adjusts the charger PWM signal output accordingly. The charger PWMoutput provides the control signal CTRL1 for the charger 116 (FIG. 8)and/or CTRL3 and CTRL4 for the bidirectional booster/charger 168 (FIG.11).

Charging a Lithium-Iron-Phosphate (LiFePO₄) battery requires precisemonitoring and control. During an initial charging phase, the chargingsubsystem controls the PWM output to achieve a constant charging currentin accordance with battery specifications. As the battery becomescharged, its voltage increases steadily under constant currentconditions. Accordingly, the charging subsystem maintains a constantcharging current while monitoring the battery 120 for increasingvoltage.

Once the battery voltage reaches its target level, the chargingsubsystem modifies its output control to maintain a constant voltage onthe battery 120. During this constant-voltage phase, the chargingsubsystem adjusts the control output to hold the charger voltage steady.For a normal LiFePO₄ battery charged with this method, the chargecurrent will steadily decrease during the constant voltage phase.

During the constant voltage (CV) phase, the charging subsystem monitorsthe charger current, and stops charging when the charging current dropsbelow the CV minimum charging current threshold. The microcontroller 110updates a status flag register to “charged” and continues to monitor thebattery voltage. The charging algorithm reverts to charging (startingwith constant current) in the event that the battery voltage drops belowa “turn on charger” threshold. In some embodiments, the microcontrollermay wait until the “turn on charger” threshold has been sustained for acertain period of time, such as minute, before charging is resumed.

Accordingly, some embodiments provide a microcontroller-controlledcharging control loop for a rechargeable battery in an emergencylighting module for a solid state luminaire. The microcontroller mayimplement a charging algorithm specifically tailored for a LiFePO₄battery; however, the charging algorithm may be adapted to any batterytechnology needs. The charging algorithm may utilize only a portion ofthe microcontroller's feature set and bandwidth for charging, so thatthe microcontroller may perform many other tasks concurrently withbattery charging. Moreover, the charging algorithm may utilize acontrolled ramp up of the charging signal to simplify and/or replace ahardware control loop.

With the wide variety of lumen levels supported in luminaires with whichan emergency lighting module may be used, it may not be cost effectiveto use a single battery pack to support all of them. A single batterypack would have to be sized to support luminaires with the highest lumenrating, and may be significantly oversized for luminaires with lowerlumen ratings.

One solution is to use multiple battery packs much more tailored to meetthe needs of a narrower range of applications. To reduce inventory andcost, it is desirable to use the same emergency lighting moduleelectronics to support a variety of different battery packs. In order toaccomplish this, it is desirable for the microcontroller of theemergency lighting module to be able to identify the battery capacity.

Methods for generating the battery type signal BT are illustrated inFIGS. 12A to I²C, and may include, but are not limited to, the use of anI²C communication channel between the battery 120 and the emergencylighting module 100 (FIG. 12A). The I2C channel is implemented using aprogrammable device 180 in the battery 120 which communicates with theemergency lighting module using POWER, CLOCK, DATA and GROUND lines. Inother embodiments, fixed interface lines tied to either a logic ‘1’ or alogic ‘0’ such that they may be read back by a digital controller (FIG.12B) may be used. In the example shown in FIG. 13B, two of the datalines are tied to logic ‘1’, while one is tied to logic ‘0’. With threedata lines, up to eight different battery types can be recognized. Instill further embodiments, a fixed resistor to which a current may beapplied and the voltage read back by a microcontroller in the emergencylighting module 100 (FIG. 12C) is used to identify the battery 120. Anyof these approaches may enable the microcontroller 110 to identify thetype or model of battery that is connected to the emergency lightingmodule 100 and to adjust the charging and boosting algorithms of theemergency lighting module accordingly.

An alternative method of providing the BT signal is via configurationduring product assembly. For this method, when the Printed Wiring BoardAssembly (PWBA) containing the ELM microcontroller 110 is to be combinedinto a system with a known battery input, the microcontroller receivesconfiguration information about the battery specification, and storesthat information in non-volatile memory, for use by its controlalgorithms during emergency operation.

The life span of the battery 120 is expected to be significantly lessthan the life of the luminaire or emergency lighting module with whichit is used. In order to further reduce cost and increase the servicelife of luminaires and emergency lighting modules, an emergency lightingmodule according to some embodiments includes a field replaceablebattery pack.

Referring to FIG. 13, which is an exploded perspective view of aluminaire 70 including an emergency lighting module 100, a housing 200houses LED control circuitry 50 and the emergency lighting module 100.An AC/DC converter 40 may also be enclosed within the housing 200. Abattery 120 is mounted in a battery cage 210, which may be installedwithin the housing 200. A lid 220 may be placed over the housing tocover the components mounted therein, and a cover retainer 215 may beplaced over the cover 220 to hold the cover 220 in place. When the coverretainer 215 and the cover 220 are removed, the battery 120 may beexposed for field replacement by a service technician.

By monitoring the AC line voltage, an emergency lighting moduleaccording to some embodiments may automatically detect loss of AC powerand transition smoothly to emergency lighting operation in which poweris supplied to the luminaire from the battery.

Solid state light sources are most efficiently driven from voltages thatare nominally much greater than voltages generated by most batterypacks. Battery packs are most efficient and cost effective when limitedto two to four cells. In order to achieve increased efficiency for bothdevices it is desirable to use a voltage boosting circuit to step thebattery voltage up to levels required to drive the LEDs. To simplify theemergency lighting control algorithm, it is desirable to control thetransitions to and from battery power. In some embodiments, the batterybooster voltage may be gradually increased when transitioning to batteryoperation. Likewise, the battery booster voltage may be gradually rampeddown when transitioning off of battery operation. This allows gradualtransition of load between the battery booster and the AC/DC converter.

FIGS. 14A-C illustrate an example of a transition from normal operationto emergency operation and back to normal operation. FIG. 14A is a graph272 of an exemplary DC_IN voltage generated by an AC/DC converter 40. Asshown therein, the voltage DC_IN is generated by the AC/DC converter 40at a voltage level V0. In some embodiments, V0 may be about 37 Volts;however, the level of V0 is dependent on the configuration of the LEDcontrol module 50 and the LED board 60. In general, for solid statelighting applications, V0 may bet between about 15 and 500 Volts.

At time T0, the AC line voltage input to the AC/DC converter 40 fails,at which point the DC voltage DC_IN begins to ramp down as capacitancein the AC/DC converter 40 discharges. At time T1, the AC line voltage isrestored, at which point the voltage DC_IN begins to ramp back up to theV0 level.

FIG. 14B is a graph 274 of booster voltage DC_OUT generated by a voltagebooster 118 or a bidirectional boost/charger 168 upon transition tobattery power (emergency mode) and back to line power. Referring to FIG.14B, at time T0, the microcontroller 110 detects a loss of AC linevoltage. The loss of AC line voltage is detected directly from the linevoltage or from a rectified AC output by the AC/DC converter 40 to theemergency lighting module 100. Thus, the emergency lighting module maydetect loss of AC power before the DC voltage DC_IN output by the AC/DCconverter 40 has dropped too far.

FIG. 14C is a graph 276 of the voltage VDC that is actually applied tothe LED control module 50. As shown in FIGS. 4 and 5, the voltage VDCmay be the diode-OR'ed product of DC_IN and DC_OUT. Accordingly, thevoltage VDC may take the value of whichever of DC_OUT and DC_IN isgreater.

Referring again to FIGS. 14A-C, when emergency mode is entered at timeT0, the microcontroller 110 causes the voltage booster 118 orbidirectional boost/charger 168 to begin generating a boosted outputvoltage DC_OUT. The level of DC_OUT increases from time T0 up to amaximum level V0, which may be equal to the level of DC voltage thatwould otherwise be supplied by the AC/DC converter 40 of the luminaire70. The voltage level VDC supplied to the LED control module 50 may dip278 when the DC_IN voltage drops. However, the DC_OUT voltage may beginto ramp up quickly enough that the voltage level VDC supplied to the LEDcontrol module 50 does not drop too far. For example, the DC_OUT voltagemay ramp up quickly enough that the increasing level of DC_OUT exceedsthe dropping value of DC_IN before the value of DC_IN drops by more thana predefined level ΔV, which may be about 4 Volts for a 37 Volt system.Ramping the voltage DC_OUT up to V0 may take about 0.1 to 4 seconds, andin some embodiments between about 0.01 and 100 seconds. Accordingly, theramping rate up to V0 may be about 1 to 40 V/s. The DC_OUT level ismaintained throughout emergency lighting operation until the battery isdischarged or AC line power is resumed.

In the example illustrated in FIG. 14, the microcontroller 110 detectsthe resumption of AC line voltage at time T1. At that time, themicrocontroller causes the voltage booster 118 or bidirectionalboost/charger 168 to begin ramping the voltage back down as the voltageDC_IN begins to ramp back up. However, ramping down the DC_OUT voltagemay be delayed slightly to ensure that there is only a slight dip 279 inthe VDC signal. Ramping the voltage back down from V0 may take about0.01 to 100 seconds. A manufacturer may desire to use an emergencylighting module as described herein in connection with many differenttypes of luminaires. Thus, it is desirable for an emergency lightingmodule to support different lumen levels for different applications.

In some embodiments, the luminaire 70 provides a feedback signal MT tothe emergency lighting module 100, 100′ which indentifies the luminairemodel, and which may be used by the emergency lighting module 100, 100′to determine the lumen level of the luminaire 70. Based on the lumenlevel of the luminaire 70, a PWM_OUT signal is generated to drive theluminaire at a desired lumen level for emergency lighting operation.This enables a single emergency lighting configuration to supportmultiple different lumen level luminaires and provide the same lumenlevel during emergency operation regardless of the lumen rating of theluminaire to which the emergency lighting module 100, 100′ is connected.

For example, if the desired emergency lighting level is 1000 lumens, aluminaire 70 rated at 4000 lumens may be driven by the emergencylighting module 100, 100′ at a fixed PWM duty cycle corresponding to1000 lumen operation. A luminaire rated at 2000 lumens may be driven ata different PWM duty cycle for the same 1000 lumen operation. Thisconfiguration promotes consistent emergency operation with the samebattery size.

Methods for generating the module type signal MT are illustrated inFIGS. 15A to 15C, and may include, but are not limited to, the use of anI²C communication channel between the luminaire 70 and the emergencylighting module 100 (FIG. 15A). The I2C channel is implemented using aprogrammable device 180 in the luminaire 70 which communicates with theemergency lighting module using POWER, CLOCK, DATA and GROUND lines. Inother embodiments, fixed interface lines tied to either a logic ‘1’ or alogic ‘0’ such that they may be read back by a digital controller (FIG.15B) may be used. In the example shown in FIG. 12B, two of the datalines are tied to logic ‘1’, while one is tied to logic ‘0’. With threedata lines, up to eight different luminaire types can be recognized. Instill further embodiments, a fixed resistor to which a current may beapplied and the voltage read back by a microcontroller in the emergencylighting module 100 (FIG. 15C) is used to identify the luminaire 70. Anyof these approaches may enable the microcontroller 110 to identify thetype or model of luminaire to which the emergency lighting module 100 isconnected, and thereby infer the rated lumen level of the luminaire.

It will be appreciated that in place of an I²C connection, an Ethernet,synchronous or asynchronous serial or parallel interface, or any othercommunication protocol may be employed.

An alternative method of providing the MT signal is via configurationduring product assembly. For this method, when the Printed Wiring BoardAssembly (PWBA) containing the ELM microcontroller is to be combinedinto a system with a known light output, the microcontroller receivesconfiguration information about the light output requirement, and storesthat information in non-volatile memory, for use by its controlalgorithms during emergency operation.

While in emergency lighting mode, the emergency lighting module monitorsthe battery voltage and current while driving the LED control module 50via the dimmer pulse width modulation signal PWM_OUT generated by themicrocontroller 110.

FIG. 16 is a graph of duty cycle versus time for a PWM signal generatedby a microcontroller 110 of an emergency lighting module 100 accordingto some embodiments. When switching to battery power, themicrocontroller 110 may start the dimmer PWM_OUT signal at a low initialduty cycle (for example about 1%), and may thereafter ramp the PWM_OUTsignal to a desired duty cycle, (e.g., 35%) shown in FIG. 15 as TARGET.Ramping the PWM_OUT signal may avoid start-up issues with the drivercircuit in the LED control module 50. Once the microcontroller 110 hasramped the PWM_OUT signal to the target duty cycle, the target dutycycle is maintained for an initial period, which may in some cases beabout three minutes. At the end of the initial period, themicrocontroller 110 may begin a gradual ramp down of the duty cycle toachieve a final PWM duty cycle of nominally 60% of the target duty cycleat ninety (90) minutes after the emergency lighting module 100 enteredthe emergency lighting mode. For example, if the target duty cycle is35%, the ending duty cycle will be about 21% at the 90 minute mark. Theramp down may be linear, quasi-linear, parabolic, piecewise linear,exponential, or may follow any other waveform. The final PWM_OUT dutycycle is maintained until either power is re-applied, or the batterydrops below the fully-discharged level. If the battery level drops tothe fully discharged level, the microcontroller 110 shuts down the lampdrive and enters low power mode until power is restored.

The ramp down of the PWM_OUT dimming signal described above meets theUnderwriters Laboratories UL924 standard requirement that the finallight output of an emergency egress light be 60% of the initial value.In addition, by ramping down the dimming, the emergency lighting module100 conserves power, which allows for a smaller capacity battery (andlower cost) than would be required if the dimming signal were heldsteady for the entire 90 minutes.

Ramping down the PWM_OUT dimming signal causes the light emitted by theluminaire 70 to decrease over time, which provides a visual indicator tobuilding occupants that the emergency lighting power is decreasing,which may encourage occupants to exit the building sooner.

With the use of a digital controller additional operational improvementscan be made by sensing the light output and/or temperature of theluminaire 70 directly. The LED string current and voltage may beadjusted in response to sensor measurements to maintain optimalefficiency and light output quality.

In some further embodiments, the power good output of the lightingcontroller may be monitored by the emergency lighting controller 100,which may respond to abnormal conditions and improve overall efficiencyand reliability.

Referring again to FIG. 6, an emergency lighting module 100 according tosome embodiments includes a test switch 135 that may be used to initiatetest operation of the emergency lighting module 100. Implementation oftest functions may be necessary to comply with product certificationrequirements. The emergency lighting module 100 may also include astatus indicator 140, which may be an LED status indicator, that canprovide feedback to the user as to the status of the emergency lightingmodule, the level of charge currently available on the battery, etc.Charge status of the battery may be indicated, for example, by flashingan indicator lamp at an increasing rate as the battery takes morecharge, by providing a series of indicator lamps and progressivelylighting indicator lamps in the series until the battery is charged,etc.

The emergency lighting module test switch subsystem includes the testswitch 135 and the microcontroller 110 which implements an algorithm formanaging the test switch 135.

In some embodiments, the microcontroller 110 may respond to actuation ofthe test switch by initiating a battery test only if the battery isfully charged. However, in other embodiments, the battery may not needto be fully charged before a test is initiated.

From an initial state, the microcontroller may measure the duration of atest switch signal. When the test switch is de-actuated (e.g., apushbutton switch is released), the microcontroller may activate eithera “monthly” or “yearly” test, depending on duration of the test switchactuation. The monthly test may be a brief (e.g. thirty second) test toensure that the luminaire will operate on battery power in response to aloss of the AC line voltage. The yearly test may be a more thorough testthat verifies the luminaire will continue to run for a full ninetyminutes on battery power after loss of the AC line voltage.

For example, if the test switch is actuated momentarily (e.g., apushbutton switch is held down for less than ten seconds), themicrocontroller 110 may initiate the “monthly” test; if the button isactuated for more than ten seconds, the microcontroller 110 may initiatethe more exhaustive “yearly” test. In other embodiments, if the buttonis held down for more than a predefined period of time, the emergencylight module will begin a test that operates only so long as the buttonis held down.

Once a battery test is initiated, the microcontroller 100 may activate afive second timer during which it ignores additional button presses (the“cancel lock-out period”).

Subsequent the cancel lock-out period, the microcontroller 110 mayresume monitoring the test switch 135. If the user actuates the testswitch after the 5-second cancel lock-out period has elapsed, themicrocontroller 110 may proceed to cancel the battery test.

If the battery test fails, the microcontroller may place the emergencylighting module 110 in a “fail wait” state until the test switch 135 hasbeen pressed and released.

If the test switch 135 is actuated for more than ten seconds, theemergency lighting module 100 may switch to emergency (battery power)mode for a full ninety minutes.

The microcontroller 110 may be configured to ignore requests to initiatebattery testing unless the battery is fully charged and the AC linevoltage is present.

Test switch handling is illustrated, for example, in the flowchart ofFIG. 17. As shown therein, the microcontroller 110 monitors the statusof the test switch 135 (block 302). If the switch is activated (block304), operations proceed to block 306. Otherwise, the microcontroller110 continues to monitor the status of the switch.

After activation of the switch, at block 306, the microcontroller 110checks to see if the battery 120 is fully charged. If not, themicrocontroller ignores the switch, and operations return to block 302to continue to monitor the switch status.

If the battery is fully charged, the microcontroller 110 then checks tosee if the switch was actuated for more than a threshold time, such asfor more than ten seconds (block 308). If not, a monthly test isinitiated (block 310), and if so, a yearly test is initiated (block312).

The microcontroller then starts a cancel lockout period, such as fiveseconds, during which time it ignores further button presses (block314). After the end of the lockout period, the microcontroller 110 againmonitors the switch status (block 320). If the switch is activatedagain, the microcontroller 110 will cancel the current test (block 322).If the switch is not activated, the microcontroller checks to see if thetest is complete (block 324), and if not returns to block 320 to checkthe status of the test switch at block 320. If the test is complete, theoperations of FIG. 17 may be restarted from the beginning.

The battery testing simulates an on-battery (i.e., emergency lighting)scenario. In a yearly test scenario, the emergency lighting module 100operates as described above, ramping from the initial value to 60% ofthe initial value over the course of the 90-minute battery test.

Although described above as a pushbutton switch, the test switch 135 maybe implemented in a number of different ways, as illustrated in FIGS.18A-18D. In particular, some embodiments provide a wireless interfacefor actuating the test switch 135. Referring to FIG. 18A, the testswitch 135, which is coupled to the microcontroller 110 in an emergencylighting controller 100, may be actuated by an infrared receiver 360A inresponse to an infrared signal 355A transmitted by an infraredtransmitter 350A.

Similarly, referring to FIG. 18B, the test switch 135 may be actuated bya Bluetooth receiver 360B in response to a Bluetooth signal 355Btransmitted by a Bluetooth transmitter 350B.

Referring to FIG. 18C, the test switch 135 may be actuated by a WIFIreceiver 360C in response to a WIFI signal 355C transmitted by a WIFItransmitter 350C.

Referring to FIG. 18D, in other embodiments the test switch 135 may beactuated by a visible light detector 360D in response to a visible lightsignal 355D transmitted by a light emitting device 350D, such as aflashlight, laser pointer, etc.

Providing a wireless interface to a test switch of an emergency lightingmodule may be particularly beneficial for installations where theluminaire is mounted out of reach, so that a technician is not requiredto physically climb up to the location of the luminaire in order tomanually engage a pushbutton switch.

Referring again to FIG. 6, the emergency lighting module 100 may furtherinclude a status indicator 145, which may include one or more lightemitting diodes of different colors.

Using the status indicator 145, the emergency lighting module 100 maydisplay information about various machine conditions, including batterycharging, battery charged, battery test in progress, “on battery” (i.e.,emergency) operation, battery failure, etc.

In some embodiments, the status indicator 145 may include one red andone green LED for indicating the state of the emergency lighting module100. With two LEDs, there are many possible combinations of distinct LEDflashing sequences, allowing greater detail to be displayed and easilyinterpreted. For example, an alternating red and green pattern may beused for indicating a test sequence. Table 1 lists several possible LEDindicator combinations for use in the emergency lighting application.

TABLE 1 Status Indicator Key ELM State LED State AC present, Batteryfully GREEN ON charged (includes trickle charge) RED OFF AC present,Battery charge GREEN FAST BLINK in progress RED OFF AC present, Test inprogress Alternate blinking RED/GREEN AC present, Test complete: BatteryTest Passed = back to battery charge in progress state (GREEN FASTBLINK, RED OFF) Battery Test Failure = GREEN OFF, RED FAST BLINK AC notpresent, running on GREEN OFF battery RED SLOW BLINK Fatal Error BatteryLow GREEN OFF RED Double BLINK Fatal Error (Other) GREEN OFF RED TripleBLINK Pushbutton Stuck Low GREEN Double BLINK RED OFF Non-Fatal Error(Other) GREEN Triple BLINK RED OFF Stuck in Initial State Green Toggle(on/off) (VSEC below threshold) RED OFF

In other embodiments, the status indicator may include an alphanumericLCD display that can display status information alphanumerically undercontrol of the microcontroller 110.

In many environments, dimming is an important feature for a lightfixture to implement. Various different dimming technologies have beendeveloped for both incandescent and fluorescent lighting, whichrepresent the vast majority of installed commercial lighting facilitiestoday. As solid state lighting fixtures are developed and become moreavailable as a replacement technology for incandescent and fluorescentlighting, it is desirable for solid state luminaires to respondappropriately to dimming signals generated by various different types ofdimming systems.

One rudimentary method of dimming control is referred to as stepdimming. Step dimming uses multiple switches that allow a user to selectone of several (e.g., two or three) different brightness levels for alight fixture by appropriate setting of multiple switches. For example,in a three-bulb fluorescent fixture, one switch may control the twoouter bulbs, while another switch may control the single inner bulb. Bysetting the switches appropriately, the user can turn on one, two, threeor no bulbs in the fixture at one time, effectively providing fourlevels of dimming.

0-10 V dimming is an electronic lighting control signaling system thatenables continuous dimming between brightness levels. A 0-10V dimmingswitch generates a DC voltage that varies between zero and ten volts inresponse to a user setting, such as the position of a slide switch or adial connected to a potentiometer. The controlled lighting fixturetypically scales its output so that it emits full brightness in responseto a 10 V control signal and is off (zero brightness) in response to a 1V control signal. Dimming devices may be designed to respond in variouspatterns to the intermediate voltages, such as giving output curves thatare linear for voltage output, actual light output, power output,perceived light output, etc.

Dimming fluorescent ballasts and dimming LED drivers often use 0-10 Vcontrol signals to control dimming functions. In many cases, however,the dimming range of the power supply or ballast is limited.

Digital Addressable Lighting Interface (DALI) is a technical standardfor network-based systems that control lighting in buildings. It wasestablished as a successor for 0-10 V lighting control systems. The DALIstandard, which is specified in the IEC 60929 standard for fluorescentlamp ballasts, encompasses the communications protocol and electricalinterface for lighting control networks. A DALI network consists of acontroller and one or more lighting devices (e.g., electrical ballastsand dimmers) that have DALI interfaces. The controller can monitor andcontrol each light by means of a bi-directional data exchange. Data istransferred between controller and devices by means of an asynchronous,half-duplex, serial protocol over a two-wire differential bus.

A luminaire may be designed to respond to multiple types of dimmingcontrol signals including, for example, step dimming control signals,0-10V dimming control signals, DALI dimming control signals, and otherdimming control signals. In addition, a luminaire may be designed torespond to a PWM_OUT dimming signal generated by an emergency lightingmodule as disclosed above.

FIG. 19 illustrates an emergency lighting controller 500A according tosome embodiments that is connected to a power board 400A of a luminaireaccording to some embodiments. The power board 400A includes the AC/DCconverter 40, 40′ and the LED control module 50 described above inconnection with FIGS. 4 and 5, but does not include the LED board 60 ofthe luminaire. The emergency lighting module 500A may be configured in asimilar manner as the emergency lighting modules 100, 100′ describedabove, except that the emergency lighting module 500A is additionallyconfigured to output a dimming signal source select signal SELECT to theLED board 400A as described in more detail below.

The LED board 400A may be configured to handle dimming signals generatedby many different types of dimming systems, including step dimming,0-10V dimming, DALI dimming, and/or other types of dimming signals. Forexample, the LED board 400A may include a step dimming interface 410that detects the presence of AC signals on multiple switched AC linescorresponding to the state of one or more step dimming switches. The LEDboard 400A may also include a 0-10V interface 420 that is configured toprocess a 0-10V dimming signal. Alternatively or additionally, the LEDboard 400A may also include a DALI dimming interface 430 that isconfigured to communicate with a DALI controller (not shown) and toreceive and process DALI dimming signals.

The step dimming interface 410 may include one or more AC detectors thatdetect the presence of AC voltage on multiple switched lines based on ACsignals provided by the AC filter 114 in the emergency lighting module500A. In response, the step interface 410 is configured to generate aPWM signal indicative of the state of the switched lines to amultiplexer 440. For example, in the case of two switched lines, thestep interface 410 may generate a PWM signal having a duty cycle of 100%if both switched lines are powered, a PWM signal having a duty cycle of50% if only one switched line is powered, and a duty cycle of 0% ifneither switched line is powered. Other arrangements are also possible.For example, the step interface could generate a PWM signal having aduty cycle of 30% if switched line 1 is powered and switched line 2 isunpowered, and a PWM signal having a duty cycle of 60% if switched line1 is unpowered and switched line 2 is powered.

The 0-10V interface 420 is configured to detect the voltage levelprovided by a 0-10V dimmer and generate a PWM signal having a duty cyclerelated to the level of the 0-10V signal. For example, the duty cycle ofthe PWM signal generated by the 0-10V interface 420 could be directlyproportional to the voltage level of the 0-10V signal (e.g., generates a50% duty cycle in response to a 5V signal, a 60% duty cycle in responseto a 6V signal, etc.). In other embodiments, the duty cycle of the PWMsignal may be related in a linear or nonlinear fashion to the voltagelevel of the 0-10V signal in order to provide, for example, PWM signalsthat result in linear changes in voltage output, actual light output,power output, perceived light output, etc., of the luminaire. The PWMsignal output by the 0-10V interface 420 is provided as an input to themultiplexer 440.

The DALI interface 430 may include circuitry for communicating with aDALI controller using asynchronous, half-duplex, serial protocol over atwo-wire differential bus, and processing the DALI signals to generate aPWM signal in response to dimming commands received over the DALIinterface. The PWM signal output by the DALI interface 430 is alsoprovided as an input to the multiplexer 440.

It will be appreciated that in a particular installation, only one typeof dimming control will be available. Thus, the multiplexer 440 willreceive only one PWM input from the step interface 410, the 0-10Vinterface 420 and the DALI interface 430. The DALI interface may be astandard DALI interface. The 0-10V interface may include an analog todigital converter that converts an analog 0-10V signal to a digitalsignal and a microcontroller that reads the digital signal andresponsively generates a PWM signal that is provided to the multiplexer440. Similarly, the step interface may include analog and/or digitalcircuitry that converts a step voltage signal to a PWM signal. Thedesign of such interface circuits is well known in the art.

The PWM dimming control signal PWM_OUT generated by the microcontroller110 is also provided as an input to the multiplexer 440. The multiplexer440 selects a PWM dimming control signal from either the PWM_OUT signalgenerated by the microcontroller 110 on the one hand or an available oneof the PWM signals generated by the step interface 410, the 0-10Vinterface 420 or the DALI interface 430 on the other hand and suppliesthe selected PWM signal to the LED control module 50 in response to theSELECT signal output by the microcontroller 110. Accordingly, in theevent of a power loss, dimming control of the luminaire may be takenover by the emergency lighting module 500A. In that case, dimming of theluminaire is based on the PWM_OUT dimming signal output by themicrocontroller 110, and any dimming signal generated by the normaldimming system (e.g., step, 0-10V or DALI) is disregarded by theluminaire.

An emergency lighting controller 500B and a power board 400B of aluminaire according to further embodiments are illustrated in FIG. 20.The emergency lighting controller 500B and power board 400B shown inFIG. 20 are similar to the emergency lighting controller 500A and powerboard 400A shown in FIG. 19, except that in the embodiments illustratedin FIG. 20, some of the dimming control functionality is moved to theemergency lighting controller 500B.

Referring to FIG. 20, the emergency lighting controller 500B includes ananalog to digital converter 510 that receives the 0-10V signal from a0-10V dimmer (not shown) and generates a digital value that isproportional to the level of the 0-10V signal. It will be appreciatedthat the ADC 510 can be integrated in the microcontroller 110 and/orimplemented as a separate peripheral component thereof. The emergencylighting controller 500B also includes separate AC detectors 512A-5I2Cfor detecting the presence of AC voltage on multiple switched lines(switched line 1 and switched line 2) as well as an unswitched AC line.The microcontroller 110 can determine the state of a step dimmingcontrol based on the detected presence or absence of AC voltage on theswitched lines.

The microcontroller 110 may therefore generate the PWM_OUT dimmingsignal in response to a step dimming signal, a 0-10V dimming signal, orin response to a loss of AC power on the unswitched AC line. The PWM_OUTsignal may therefore be generated by the emergency lighting module 500Bduring normal operation, and not just during emergency operation.However, since the power board 500B still includes a DALI interface 430,the microcontroller 110 still generates a SELECT signal to cause themultiplexer 440 to select between the PWM_OUT signal generated by themicrocontroller 110 and the PWM signal generated by the DALI interface430. A jumper setting in the emergency lighting module 500B may be usedto indicate to the microcontroller 110 which type of dimming control isbeing used. In other embodiments, configuration data that is written toa programmable device at the time of manufacture may be used to identifythe type of dimming control that is used.

An emergency lighting controller 500C and a power board 400C of aluminaire according to further embodiments are illustrated in FIG. 21.The emergency lighting controller 500C and power board 400C shown inFIG. 21 are similar to the emergency lighting controller 500B and powerboard 400B shown in FIG. 20, except that in the embodiments illustratedin FIG. 21, all of the dimming control functionality is moved to theemergency lighting controller 500C.

Referring to FIG. 21, the emergency lighting controller 500C includes aDALI interface that communicates with a DALI controller (not shown) toreceive and process DALI dimming control commands. In this embodiment,all dimming by the power board 400C is controlled by the PWM_OUT signalgenerated by the microcontroller 110. Accordingly, power board 400C doesnot include a multiplexer and the microcontroller 110 does not have togenerate a SELECT signal to control its operation.

Many different embodiments have been disclosed herein, in connectionwith the above description and the drawings. It will be understood thatit would be unduly repetitious and obfuscating to literally describe andillustrate every combination and subcombination of these embodiments.Accordingly, all embodiments can be combined in any way and/orcombination, and the present specification, including the drawings,shall be construed to constitute a complete written description of allcombinations and subcombinations of the embodiments described herein,and of the manner and process of making and using them, and shallsupport claims to any such combination or subcombination.

In the drawings and specification, there have been disclosed typicalembodiments of the invention and, although specific terms are employed,they are used in a generic and descriptive sense only and not forpurposes of limitation, the scope of the invention being set forth inthe following claims.

What is claimed is:
 1. An emergency lighting module for providingemergency power to a solid state luminaire, the emergency lightingmodule comprising: a microcontroller; and a detector coupled to themicrocontroller and configured to detect a status signal indicative of astatus of an AC line voltage, wherein the emergency lighting module isconfigured to output a dimming control signal to the solid stateluminaire in response to the status signal.
 2. The emergency lightingmodule of claim 1, wherein the microcontroller is further configured tooutput a select signal to the solid state luminaire to cause the solidstate luminaire to dim in accordance with the dimming control signalwhen the dimming control signal is output.
 3. The emergency lightingmodule of claim 2, wherein the microcontroller is configured to causethe solid state luminaire to select from among step dimming, 0-10Vdimming and/or digital addressable lighting interface (DALI) dimmingusing the select signal.
 4. The emergency lighting module of claim 2,wherein the microcontroller is configured to cause the solid stateluminaire to select from among step dimming, 0-10V dimming, digitaladdressable lighting interface (DALI) dimming, and/or pulse widthmodulation (PWM) dimming using a PWM signal generated by the emergencylighting module using the select signal.
 5. The emergency lightingmodule of claim 1, wherein the status signal indicates a reduction orinterruption of the AC line voltage.
 6. The emergency lighting module ofclaim 1, wherein the emergency lighting module is further configured tooutput a step dimming control signal to the solid state luminaire inresponse to the presence or absence of one or more AC line inputsignals.
 7. The emergency lighting module of claim 1, further comprisingan AC filter coupled to the detector and configured to supply a filteredAC signal to the detector, wherein the AC filter is configured to outputthe step dimming control signal to the solid state luminaire.
 8. Theemergency lighting module of claim 1, further comprising: an inputconfigured to receive an external dimming signal and to generate thedimming control signal in response to the external dimming signal whenno reduction of the AC line voltage is detected.
 9. The emergencylighting module of claim 8, wherein the dimming control signal comprisesa pulse width modulation (PWM) signal.
 10. The emergency lighting moduleof claim 9, further comprising a digital addressable lighting interface(DALI) interface configured to receive a DALI dimming signal, whereinthe external dimming signal comprises the DALI dimming signal.
 11. Theemergency lighting module of claim 9, wherein the external dimmingsignal comprises a 0-10V signal or a step dimming signal.
 12. Theemergency lighting module of claim 11, further comprising a plurality ofAC detectors configured to detect a presence or absence of a pluralityof switched AC line voltage signals and to generate the step dimmingsignal in response to the presence or absence of the plurality ofswitched AC line voltage signals.
 13. The emergency lighting module ofclaim 11, further comprising an analog to digital converter configuredto receive the 0-10V signal and to responsively output a digital signalindicative of the 0-10V signal to the microcontroller.
 14. An emergencylighting module for providing emergency power to a solid stateluminaire, the emergency lighting module comprising: a microcontroller;an AC detector coupled to the microcontroller and configured to detect apresence of an AC line voltage, wherein the emergency lighting module isconfigured to output a dimming control signal to the solid stateluminaire in response to a reduction of the AC line voltage; and aninput configured to receive an external dimming signal and to generatethe dimming control signal in response to the external dimming signalwhen no reduction of the AC line voltage is detected.
 15. The emergencylighting module of claim 14, wherein the dimming control signalcomprises a pulse width modulation (PWM) signal.
 16. The emergencylighting module of claim 15, wherein the external dimming signalcomprises a 0-10V signal, a step dimming signal, and/or a digitaladdressable lighting interface (DALI) signal.
 17. The emergency lightingmodule of claim 16, further comprising a plurality of AC detectorsconfigured to detect a presence or absence of a plurality of switched ACline voltage signals.
 18. The emergency lighting module of claim 16,further comprising an analog to digital converter configured to receivethe 0-10V signal and to responsively output a digital signal indicativeof the 0-10V signal to the microcontroller.
 19. An emergency lightingmodule for providing emergency power to a solid state luminaire, theemergency lighting module comprising: a microcontroller; a plurality ofinputs configured to receive a plurality of external dimming signals;and a dimming control output coupled to the solid state luminaire;wherein the microcontroller is configured to generate a dimming controlsignal and to output the dimming control signal to the solid stateluminaire in response to a selected one of the external dimming signals.20. The emergency lighting module of claim 19, wherein the externaldimming signals comprise a 0-10V signal, a step dimming signal, and/or adigital addressable lighting interface (DALI) signal.